JBA Headers and Exhaust Installed! :)

[ramsee1]

Thanks Joel. I didn't know if that was the case for Toyotas or not. I have an old Lexus which does the same thing and also adjusts to the way you drive.

[Air2air]

Headers typically make you run 5% or so lean. This is actually NOT compensated for in the ECU in our case.

It's because the sensor that talks to the ECU about mixture is the MAF or Mass Airflow sensor on the throttle body. Since the ECU does not know that headers are down there, it just delivers fuel in proportion to the air going into the throttle body.

How much fuel it delivers is dictated by the ECU map. The mixture settings and ignition advance must be manually reset by 3rd party software. Then, the new settings are reflashed into the ECU with a Serial cable.

My understanding is that you normally aspirated guys don't have to worry. But supercharged you could get detonation at high RPMs if you dodn't do the above...

[ramsee1]

Yeah that makes a lot of sense- How could the ecu know what's going on in the exhaust end of things. Thanks for weighing in. Nice pics on the tour of URD by the way.

[Air2air]

Thanks for the thread ramsee. Is it too loud? how do you like the sound?

[ramsee1]

In my opinion, it can't get too loud. At idle, it sounds the same. With light accelaration, you can hear the exhaust kick in a nice deep throaty sound. A little harder on the pedal and you can hear the exhaust run through the pipes. At wot and the CAI kicks in and drowns everything out. I had a chance to really get on it today. The shifts are nice and tight and like I said the truck gets up to cruising speed with ease. I dream of adding the high--pitched "beeeeeeeeeeeeeeeeeeeeeeeee" of a supercharger to the symphony of engine sounds. someday!

btw when you did the URD supercharger, was it mandatory to add their pulley? I saw they made a smaller pulley for the trd which adds 1-2 psi boost. I don't know if my math is off or not, but that seems like it would add 1/3 more hp to the mix which would be pretty phenominal.

[mooncruiser]

Air2air previously said:

Headers typically make you run 5% or so lean. This is actually NOT compensated for in the ECU in our case.

It's because the sensor that talks to the ECU about mixture is the MAF or Mass Airflow sensor on the throttle body. Since the ECU does not know that headers are down there, it just delivers fuel in proportion to the air going into the throttle body.

How much fuel it delivers is dictated by the ECU map. The mixture settings and ignition advance must be manually reset by 3rd party software. Then, the new settings are reflashed into the ECU with a Serial cable.

My uderstanding is that you normally aspirated guys don't have to worry. But supercharged you could get detonation at high RPMs if you dodn't do the above...

Doesn't the O2 sensor provide feedback to the ECU based on what it senses in the exhaust mixture?

[Air2air]

ramsee1 previously said:

btw when you did the URD supercharger, was it mandatory to add their pulley? I saw they made a smaller pulley for the trd which adds 1-2 psi boost. I don't know if my math is off or not, but that seems like it would add 1/3 more hp to the mix which would be pretty phenominal.

Ramsee yeah you have to do the pulley because you replace the whole serpentine as well. They want to try a smaller pulley with me but they are really conservative, so it'll be a month or so I think.

mooncruiser previously said:

Doesn't the O2 sensor provide feedback to the ECU based on what it senses in the exhaust mixture?

Yeah I thought the same thing moon and I can't remember what they told me about why you still have to manually override the settings. I will have toget back on this...

[FJoel]

I think the optimum ratio for combustion of gasoline is 14:1, but this is when it burns the hottest and is not good on your engine. I am sure Toyota's ECUs are not designed to run anywhere near 14:1, so like Todd said a 5% leaner mixture on a NA engine is likely not going to hurt anything. In fact, I think this 5% leaner mixture may be where you get some of that added horsepower.

Again I am no expert, but from what research I've done, proper headers actually "suck" (proper term is "scavenge") the exhaust gasses out of the cylinder, leaving more room for fresh intake air. The more air, the leaner the mixture. It is not necessarily more volume of air, but the fact that less already burned oxygen by-products are present, the higher the volume of fresh air that can replace it.

Todd can attest to this. On aircraft you have a mixture control thrown into the mix (not on the Rans Coyote I am in love with as this is injected, but the Cessna 150, 152, and 172's I used to fly). You get your max power, and notice an RPM increase, as you lean it back to 14:1. Beyond 14:1, the engine will eventually stall.

However, this will start to raise your oil temp, cylinder head temps, and will eventually burn out the valves and so on. I think if you tried to run a stock ECU with boost and headers you would definitely burn stuff. Way too much air and the ECU is only programmed to do so much. This is where companies like URD really come into play saving our @$$es. Everytime you mod something, something has to give. "For every action there is an equal and opposite reaction." We recently found this out the hard way on the trail when my buddy's 4Runner snapped a shackle off of his axle because we got him 1.5" more travel and overlooked his upper control arm play... Oops. Sorry Dan!

Oh yeah. That shackle decided if it was going down, it was taking his brake line with it. That was fun... did we ever get the pics up here of the Nissan Xterra towing two Toyota's? (I was the rear tether for down hills...)

[DEWFPO]

Just to be anally correct, the stoichiometric air/fuel mixture for a gasoline engine is ~14.7:1 (typically at idle). Lower when your generating HP & TQ, higher when your decelerating or at lean cruise.

DEWFPO

[ramsee1]

That's ok if you were being anal, you would have carried it to the hundredths spot... Tenths is only being precise